The Biases in Captive Chimpanzee Cognitive Research: First Insights From the Ape Research Index (<scp>ARI</scp>) Database

ABSTRACT Comparative studies provide crucial insights on human behaviour and our evolutionary past, ranging from the roots of human culture and cognition to understanding the mechanisms behind specific phenomena such as addiction. Chimpanzees ( Pan troglodytes ) are the primary model species for comparative cognition research. In particular, captive chimpanzees are important comparative models due to the more controlled settings provided by captivity and the generally easier access than wild populations. This reliance on captive chimpanzees has resulted in the rise of specific research‐intensive facilities that house chimpanzees which, in some cases, are tested regularly throughout their entire lifetimes. These differences in individual research experience history may not only affect performance in tasks, but also overall cognition and motivation to participate in research. The overarching aim of the Ape Research Index (ARI) project is to assess whether research participation over time results in variation in captive chimpanzee cognition and behaviour. To do so, we must first identify whether chimpanzee research participation varies at the group and/or individual level. Accordingly, for this perspectives piece, we carried out a systematic literature review to develop the largest (to our knowledge) database on captive chimpanzee cognitive experiments between 1950 and 2024. Using this (ARI) database, we identified systematic differences in both the extent and type of accumulated research experience in captive chimpanzees within and across facilities. Based on our data, we argue that the current approach in comparative research may be biassing our understanding of ape cognition, and reducing the robustness of insights drawn from these studies. Future work will involve empirically testing these biases in order to validate any behavioural variation potentially emerging from this effect.